Coal Forge Build Help

[Ghent]

Hey all, I'm fairly new to this and this is my first forge so please bear with me. I'm currently trying to decide on a design for a coal forge.

I have this old fire pit (28in diameter, 7in deep) that I plan to use as my fire pot, the metal is thin so to prevent the fire from burning through I was thinking of using cement rated for 2,200 F to coat the inside. I also want to have a table that has a hole cut in the center that the pit fits into. I have two options for the table. I can either buy a 1/4in thick steel plate from craigslist for 60$ (I would also have to cut it down to size, but I don't have the tools to do that) 

Or I can use some 3/4in thick 95inch long and 18 wide. You probably noticed that the wood is not as wide as the pit, to remedy this I would cut the wood in half and put the two sides together making it 47.5 in long and 36 in wide. My questions are, is wood a viable option? If not is there a cheaper option than the steel plate? And is there any other comments on the design?

Sorry for the horrendous formatting, also here is another photo I forgot to add

[Irondragon Forge ClayWorks]

To be honest, I think you would be better off building a JABOD forge like this one.

If you are determined to use your fire pit consider making it a side blast but don't use the 2200 degree cement but line it with clay.

[Glenn]

Priced this week at two different big box stores, a 1 x 12 x 8 foot common pine sheeting is over $21 a board, knots, splits, and bows included.  That is a rare piece of lumber. Find a better use than cutting it for a forge.

Find an old pallet at most any store for free and take it apart. More than enough wood to make a JABOD forge. Did I mention free? So get two of them in case you need one for a project later. You will also need a piece of 3/4 or 1 inch black iron pipe, and some dirt. If you can not find dirt in Upstate New York, then pay the extra money and get a bag of NEW, not used, cheap kitty litter. One bag should be enough. 

[Ghent]

I could cut the pit in half and just have a metal sheet on one side that would have a hole for the air. (see bad sketch)

[Glenn]

It may not be thick enough metal. Suggest you make the JABOD forge first so you can have a forking forge while you think about what your second forge will look like. (grin).

[Ghent]

While the wood does look quite nice it is a laminate unfortunately, so don't be fooled. I have been considering the JABOD as another option, but I have a few questions, one being, can I just use any dirt or does it need to have a lot of clay in it? Furthermore, can the size be increased without worry or are there other factors that I would have to take into account?

[Glenn]

Most any dirt will do. Any organic matter will burn out with the first couple of fires. 

If you make the forge according to the provided design, it should work. A bit larger will not hurt. You want to establish a fire ball to forge in. The forge size beyond that is usually ends up as fuel storage or a place to put tools.  

[Irondragon Forge ClayWorks]

You can make clay with cheap unscented cat litter and sand. Why cut the fire pit in half, just drill a hole in one side to fit a side blast tuyere pipe in it and clay it in or use bricks to form the fire box. Here is one I'm making for charcoal, just need to find time to clay it up.

[Charles R. Stevens]

So 7” deep can easily accommodate a bottom blast forge. Bellow are two cities of a rivit forge. One can easily weld up a tuyere and cut a hole in the bottom of the fire pit. Now from there take a 2” pipe cap and drill a 3/4” hole in the center. Now if you position it so the top of the cap is 4” below the rim you now fill the fire pit with sub soil ( the dirt about a foot down below the top soil) or an adobe mix of 1/3 clay to 2/3 sand to 1” below the top of the cap. Then form a bowl about 8” across ending 1” below the rim of your fire pit.

a side blast can also be built easy enugh. 

[Marc1]

As much as it may be tempting to turn your fire pit into a forge, I would keep the fire pit to roast marshmallows and build a coal forge using the old methods described here many times. 

If I can add to the list, without mentioning truck rotors or brake drums, I would suggest a build that was in use when I was 15 and you could go to the local hardware store and buy a brand new hand cranked blower and tuyere together with 1/2 kilo of 3mm welding rods and not go through the aggravation of the seller describing it as an antique with museum value. 

The build is for a bottom blower, and is a simple as making a table out of angle iron say 2" x2" and 3/16" thick or 1/4" if you want.  Dimensions vary,  but more or less 4' x 3' ... but it can be smaller.

4 legs, 4 sides, and the 'top' is a sheet that fits inside the top opening but is too long and so is bent to form a shallow cavity that is 6" below the top edge of your table. Use a sheet that is thin enough for you to bend by hand but not too thin for it to rust away in a few years. May be 18 or 16 gauge?

Weld tack rivet in place, cut a hole for the tuyere, improvise something to cover the sides, make some brackets for the blower and then fill the cavity with clay. You can find clay in the ground, at the bottom of rivers or water streams, and many other places I trust you can figure out. 

As you fill the table cavity with clay, you have to mold a fire pit according to what you want. I prefer 8"x7"x4", but you can have it smaller, or round, up to you. It will cost nothing to do again over and over until you get it to work for you. 

Yes, there is the question of the blower. Hair dryer is too weak, Garden blower is too much, jumping castle fan is absurd ... short of some imported hand cranked blowers from India, and the ubiquitous museum piece, I would spend about $100 on a proper electric blower by Dayton.

let us know what you do  

[ThomasPowers]

I am a bit concerned by your size comment.  What do you need a large for for?  Do you have a powerhammer or strikers that you have not told us about?  Generally when we get new people here wanting to make large forges it turns out that they often intend to make swords. Unfortunately being new to the craft they don't realize that in general you only want to heat as much steel as you can forge in one go; so a 6" hot spot will do fine.  Heating more than that degrades the steel not being worked.

If you need to heat large objects to forge, you generally need help and or powered equipment!

Learn to drive a regular car before worrying about needing a huge dump truck!

[Charles R. Stevens]

A 3/4” tuyere generally dose just fine up to 1”. I have reworked a pick into armorers srake 

[Ghent]

After some thought, I've decided to make the JABOD forge or at least a variation of it. Thanks for all the helpful input, ill keep the fire pit on hand, just in case I decide to make use of it later. I still have to work on a blower, I was thinking of either converting a hand crank grinding stone into a blower or using a cheap hair dryer, but that's for after the forge is built.

[Charles R. Stevens]

You need a way to control the air with any electric blower, and a dead mans switch is a good idea as well (old automotive floor starter switches work well for this but any momentary switch rated for your voltage and amperage works fine).